I guarantee, there's a quiet squeeze going on. That wall of .17's was an attempt to keep the pps down. MMs do that in hopes that potential buyers will stay away if they see too much resistance going forward. In large part it works, too.
However, when demand for those shares exists (.17's), MMs realize either they better fill them with NSS shares (and ultimately lose money on them), or they mad dash to yank 'em from the ask.